A2BB′X6 double perovskite become a hot spot and attract wide attention due to their stable structure, non-toxic, excellent properties, and low cost in solar cells field. In order to screen excellent double perovskite molecules, ten A2BNiX6 molecules with density functional theory were designed in this work. The structure stability, electronic and optical properties of these molecules were studied and their effects of elements at different positions on energy bands and optical properties were analyzed. The research results show that all the A2BNiX6 double perovskite were direct band gap semiconductors, which was to the benefit of the absorption of visible light. In particular, the band gap of four types of double perovskite of A2BNiF6 whose X position was F atom were 1.52-1.69 eV, which was very suitable as a light absorbing material. Optical properties research show that A2BNiF6 double perovskite are a transparent material and have a wide range of application prospects in transparent luminescent materials. Although there are some errors relative to hybrid functional, these studies provide theoretical support for light-absorbing materials for double perovskite solar cells.